Plastics are inexpensive and durable materials, which can be used to manufacture a variety of products that find use in a wide range of applications. As a consequence, the production of plastics has increased dramatically over the last decades. Moreover, more than 50% of these plastics are used for single-use disposable applications, such as packaging, agricultural films, disposable consumer items or for short-lived products that are discarded within a year of manufacture. Because of the durability of the polymers involved, substantial quantities of plastics are piling up in landfill sites and in natural habitats worldwide, generating increasing environmental problems. Even degradable and biodegradable plastics may persist for decades depending on local environmental factors, like levels of ultraviolet light exposure, temperature, presence of suitable microorganisms, etc.
Different solutions have been studied to reduce environmental and economic impacts correlated to the accumulation of plastic, from plastic degradation to plastic recycling, including reprocessing the degraded plastic in new plastic material.
As an example, in recent years, polyethylene terephthalate (PET), an aromatic polyester produced from terephthalic acid and ethylene glycol, has been widely employed in the manufacture of several products for human consumption, such as food and beverage packaging (e.g.: bottles, convenience-sized soft drinks, pouches for alimentary items) or textiles, fabrics, rugs, carpets, etc.
In parallel, PET is the most closed-loop recycled plastic. Generally speaking, PET wastes are subjected to successive treatments leading to recycled PET (rPET). PET wastes (mainly bottles) are collected, sorted, pressed into bales, crushed, washed, chopped into flakes, melted and extruded in pellets and offered for sale. Then, these recycled PET may be used to create fabrics for the clothing industry or new packaging such as bottles or blister packs, etc.
However, such plastic recycling processes are adapted to plastic items containing only PET, and thus need a prior extensive sorting. Such plastic recycling processes thus lead to downgrading applications and are also expensive, so that the recycled products are generally non-competitive compared to virgin plastic.
Another potential process for recycling plastic consists of chemical recycling allowing recovering the chemical constituents of the polymer. The resulting monomers, after purification, may be used to re-manufacture plastic items or to make other synthetic chemicals. However, up to now, such recycling process has only been performed on sorted or partially sorted polymers and is not efficient on raw plastic products that may comprise a mix of different polymers.
Thus, a need exists for an improved process for degrading plastic products that does not require preliminary sorting and/or expensive pretreatments and that may be used with industrial yield.